Of particular interest in a drinking water context, are those bacteria responsible for widespread occurrences and recurrences of intestinal infections in humans, namely, the coliform family of bacteria, e.g., E coli. These bacteria commonly contaminate drinking water supplies when waste water containing faecal material spills into a water supply, or when excessive anaerobic decay of vegetation in the water supply occurs.
Iodine has been used for water disinfection on a large scale in the past. Iodine is used commonly also for its antibiotic (sensu stricto) effects against bacteria, viruses and cysts, as these three pathogens constitute the most common health risks in maintaining biologically safe water supplies. Traditionally, crystalline iodine is dissolved in water under static conditions by the addition of small amounts of KI, which greatly enhances the dissolution of the iodine. In general, the actual inactivation mechanism of the pathogenicity of bacteria, viruses and cysts by iodine is poorly understood.
U.S. Pat. Nos. 5,919,374 and 6,139,731 describe a method and apparatus, respectively, for producing bacteria-free water containing iodine species under continuous dynamic water flow, comprising the steps of: (1) selecting a predetermined temperature; (2) heating a first water flow in the iodine chamber to the predetermined temperature; (3) providing solid iodine; (4) passing the first water flow at a first flow rate through solid iodine to dissolve said solid iodine into the first water flow to produce a saturated aqueous solution containing iodine species at the predetermined temperature; and; (5) blending the saturated solution with a second water flow to produce a diluted iodine species bacterium-free aqueous solution.
Practical application of this technology involved a device which was hydraulically coupled while the blending of the saturated iodine solution with mainline water was accomplished by utilizing back pressure to drive a stream of water through the iodine generating system.
It is known that under field conditions, e.g. in the barns and fields of factory farmed livestock, drinking operation flow rates fluctuate depending on peak demand and the age of the animals. No matter how many animals are housed in a barn, they tend to drink water at specific times during the day and establish peak water demand periods. In off-peak periods, water demand or flow rate in the system can fall off to the point where adjustments to the mainline valve in commercial systems are required in order to compensate for low water demand. This is particularly so with young animals, which do not draw a lot of water, even during peak demand periods. It has been found with adult animals, that the changes in water demand from peak to off-peak conditions do not substantially alter the concentration level of the diluted aqueous iodine solution, provided the concentration level of the saturated iodine solution is near constant and animal stocking densities are sufficient to provide minimum pressure requirements during off-peak periods. However, if water flow rate does drop below about 4 liters per minute, which often happens with young animals, or if flow rate during the off-peak period drops substantially below peak demand, which can happen with adult animals when stocking densities are low, there may be insufficient pressure to control the production of a consistent concentration of diluted aqueous iodine. Although these conditions can be manually controlled, such control requires constant monitoring by an operator, which is a situation that is not feasible in a livestock operation.
Additionally, as it is essential to maintain a minimum water pressure in barns in order to deliver sufficient quantities of water to the animals, the number and type of inline devices is an important consideration to the livestock grower. Cumulative pressure drops across the system will fluctuate dependent upon such factors as particle loading in filters or the addition of inline devices. This cumulative effect sometimes reduces overall water pressure below that which is required in order to deliver a consistent level of iodine. More importantly to the grower, this cumulative effect means that the animals are not receiving sufficient quantities of water.
Practical experience has shown that desired control of the addition of a solution of known concentration to a main line flow is not readily attainable since with back-pressure dependent delivery systems high pressure drops may be created during operations to produce unwanted hysterisis curves for chemical species since consistent reproducibility is essentially independent of water flows extending from new zero to very high flow rates.
Further, since cumulative pressure drops in a barn environment would not be accepted by the industry, in low pressure situations, pressure drops inherent in certain control systems could inhibit the flow of water and thereby prevent certain valve systems from operating.
It is most important, commercially, that a practical and reliable “fail-safe” control and delivery mechanism be employed. A non-reliable “fail-safe” system could result in either a flood or a shut down of the water supply to the animals, which could cause the death of some or all of the animals.
It is also important commercially that a delivery system should have an acceptable operational life span of at least 2 years and, also, not require premature extensive repairs or replacements.
There is a demand, therefor, for an improved drinking water delivery system that is economic, reliable and operable over the full range of practical water flow rates demanded by the livestock animals 24 hours a day.